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The oldest cancer in the world affects our dogs and is sexually transmitted

Dog lying in the covers and looking sad
© Pixabay

A recent study by Adrian Baez-Ortega at the University of Cambridge has shed light on the mysterious canine transmissible venereal tumour, which has been around for thousands of years.

By Justine Seraphin, 9 Aug 2019

Canine transmissible venereal tumour (CTVT) appeared between 4,000 and 8,500 years ago. Over time, it has spread to hundreds of thousands of dogs all over the world. And what makes this strain even more unique, is that unlike most cancers, it is sexually transmitted.

The study

CTVT first emerged in Asia and began to spread throughout the Americas as dogs migrated there. The disease causes tumours to appear around dogs’ genital areas, and is sexually transmitted between them.

Even though it’s been around for so long, researchers agree that the cancer hasn’t evolved much since the ancient dog days. Luckily, this does mean that CTVT will eventually die out, though it will take many thousands of years. It has almost completely disappeared already in first-world countries where dogs live as pets inside homes. However, countries where large populations of un-neutered or un-spayed dogs roam the streets are still heavily impacted by CTVT.

Despite looking into the genetics of the cancer, researchers don’t quite understand how or why the strain is sexually transmissible. Since it is a cancer that affects the genitals, it is thought that the route of transmission is easier, physically speaking, but no other clues have emerged.

Symptoms, diagnosis, and treatment

Though rare nowadays in the pet dog population, CTVT does still exist. It is in fact the only remaining link between North America's first domesticated dogs (who died after European colonisation), and today's modern dogs.

A dog with this kind of tumour will usually have a reddish mass in the superficial membrane of the vagina or penis. This mass can break if stimulated. Though dogs will be tempted to lick the area to relieve themselves, doing so could cause the mass to break and get infected.

A dog can be diagnosed with it through simple physical examinations or with x-rays.

The tumour will usually not migrate to other parts of the body, however, it is a progressive disease. Most cases are benign, but for the odd malignant tumour, the treatment consists of removal through surgery, radiotherapy, or chemotherapy. Usually, these treatments are effective in removing the tumour.